HELENA — A Public Service Commission request to look into money a member received from NorthWestern Energy is sparking heated debate.

One of the two Republicans on the panel is the target of the investigation — and he says the panel’s three Democrats are putting together a ‘‘political hatchet job’’ to advance the issue.

The three Democrats voted Tuesday to ask the attorney general’s opinion about money Brad Molnar took from NorthWestern Energy as part of an energy conservation effort in Billings last winter.

The exchange before the vote was heated.

At one point, Molnar told Democrat Ken Toole to ‘‘shut up.’’

The other Republican on the panel, Doug Mood, walked out of the proceeding, saying the effort was beneath the commission. He says the commission looks ‘‘petty and stupid.’’